An electrical component that needs cooling is placed in thermal contact with a thermally conductive material, also called a heat conductor device or heat sink. However, materials with good thermal conductivity (such as metal) also tend to have good electrical conductivity.
A nearby layer with good electrical conductivity is problematic when used in conjunction with high frequency devices such as for processor integrated circuits (ICs) or memory ICs operating in the Megahertz (MHz) or Gigahertz (GHz) domain. In these applications, the conducting surface of the surrounding layer acts as a radiator for source currents which are present internally in the IC. The surface can also act as a reflector of electromagnetic (EM) waves. This behaviour can interfere with the functioning of other electrical components and is, for that reason, often forbidden by regulations.
It is known to use other, non-conducting or poorly electrically conducting materials, such as ceramics. However, ceramics are relatively expensive and have, compared to electrical conductors, a generally poor thermal conductivity.
Another material that is used are polymers or plastics. Plastics are less expensive than ceramics, but have even poorer heat conducting properties.
It is noted that US 2006/047 053 discloses an electrically conductive polymer composition which also has a degree of thermal conductivity. A plurality of discrete electrically conductive elements are incorporated into the polymer composition. These elements give the polymer composition a degree of electrical conductivity that is intended to shield an IC coated with the polymer from electromagnetic interference (EMI) and/or radio frequency (RF) radiation. The IC is to be surrounded by the electrically conductive polymer composition or by a combination of the electrically conductive polymer composition and another electrical conductor so that a closed Faraday cage is formed. Heat conductor devices, or heat sinks, to which the present invention relates, typically are intended to enlarge the area of heat transfer and therefore typically cover only part of the IC and do not surround the IC. Heat sinks for high frequency components must be carefully designed to prevent acting as an antenna, which is not a concern of the shielding application of US 2006/047 053, which material is therefore generally unsuitable for use in heat sinks.
There is thus a need for a heat conductor device with good thermal conductivity for removing heat from electrical components which does not simultaneously act as a radiator or reflector in the frequency domain of the component.